Karst geoindicators of environmental change: The case of Lithuania

Abstract

Karst is the result of an epigenetic geomorphologic process that may involve rapid changes to landscapes and their physical properties, with the newly formed relief complicating regional economic development and the protection of nature. The intensity of the karst process is closely linked with the circulation of surface and groundwater, so that the parameters characterising water circulation and chemical denudation can serve as indicators of the intensity of karstification. In this article, we describe the North Lithuanian karst region, and evaluate the influence of climate and hydrological conditions on karstification. Upper Devonian gypsum and dolomites occur beneath the Quaternary sediments here. Sinkholes frequently appear where the latter are particularly thin and underlain by gypsum, suggesting that karstification is intensifying. This is perhaps related to climate change expressed by an increase in mean annual temperature and runoff, especially during warm winters. To identify the main determinants of the karst processes, monitoring was carried out between 1994 and 1999, and data on river runoff and water chemistry from 1962 to1999 were examined. From 1978 to 1999, the mean chemical denudation rate in the active gypsum karst zone was 30% higher than from 1962 to 1977, a change mirrored by the increased total volume of new sinkholes that appeared in the 1980s and 1990s. We have calculated the rate of chemical denudation and sinkhole formation in the last four decades and discuss karst activitiy as a geoindicator of environmental change.